Largusoperla difformitatem Chen, 2018

Chen, Zhi-Teng, 2018, A new fossil species of Largusoperla (Plecoptera: Perlidae) and its evolutionary implications, Zootaxa 4442 (4), pp. 572-578 : 573-575

Largusoperla difformitatem Chen , sp. nov.

Figs. 1–8 .

Description. Macropterous; body length (eXcluding antennae and cerci) ca. 9.5 mm, slender, generally yellow and patterned with dark brown ( Figs. 1, 2 ).

Head ( Figs. 3, 4 ): Head rounded, with a dark stigma covering the three ocelli, compound eyes dark. Antennae brown and hairy, only about 10 basal segments preserved. MaXillary palps slender, with a shortened apical segment, about two times longer than labial palps.

Pronotum ( Figs. 3, 4 ): Pronotum rugose, about as wide as head, mostly brown eXcept for the pale median band, near trapezoidal with obtuse anterior corners. MesothoraX and metathoraX sclerotized, nearly as wide as pronotum. Legs brown; first two tarsal segments shortest with conspicuous euplantulae.

Wings ( Figs. 1 , 5): Wings hyaline, veins brown, a subapical angle presents in all wings. Right forewing: length ca. 9.5 mm; ScP about three-fourth of forewing length, reaching ScP+RA beyond ra-rp; apical area between anterior margin and RA with one crossvein; over 13 crossveins present between ScP and the anterior margin; RP originated from middle of RA and with three branches; M forked at near apical one-third of the wing length; ra-rp not connected with the opposite crossvein rp-ma; CuA forked basal to the fork of M, with three branches; CuP simple; area between M and CuA with siX crossveins; area between CuA and CuP with four crossveins; AA1 simple, AA2 not visible. Hind wings length ca. 8.0 mm, apical veins similar to right forewing.

Abdomen ( Figs. 1-2 , 6-8): Abdomen near half the length of the body, with dark lateral marks. Posterolateral margins of tergum 9 eXtended. Sternum 9 eXtended backwards, posteromedially with a transverse lobe. Tergum 10 not well-preserved but apparently cleft, without projecting hemiterga. Paraproct broad and weakly sclerotized, length two times longer than width; left paraproct subtriangular with sharp apeX, widened at mid-length; right paraproct subtriangular with sharp apeX, constricted at mid-length. Cerci hairy and short, segments not clear.

Type material. Holotype male, No. CZT-PLE-MA2. This specimen is mostly wizened; apical halves of left foreleg and left midleg and apeX of antennae are not preserved; dorsal aspect of abdomen is not clear; wings are overlapped so only the right forewing is clear visible.

Etymology. The specific epithet means “asymmetry” in Latin, which refers to the asymmetrical paraprocts.

Syninclusions. Plant remains.

Remarks. Similar body color, wing venation and terminalia structures of the new species indicates its taXonomic inclusion in Largusoperla . The new species can be distinguished from other three known congeners by shape of the asymmetrical paraprocts and the subapical angles of wings. The paraproct shape of L. difformitatem is most similar to L. flata , however, the paraprocts of L. flata are laterally thickened, less divergent and shorter than L. difformitatem .

The asymmetrical paraprocts of L. difformitatem were not formed by the fossilization process. The outlines of the paraprocts are clearly visible and the differences between the two paraprocts are distinctive. In addition, asymmetrical paraprocts also occurs in other species of Largusoperla being described by colleagues elsewhere. The asymmetry of genitalia is a possible plesiomorphic character of the genus Largusoperla and perhaps for the Acroneuriinae in general.

Figures

FIGURE 1–2. Largusoperla difformitatem, sp. nov. Adult habituS, 1, dorSal view; 2,ventral view.

FIGURE 3–4. Largusoperla difformitatem, sp. nov. 3, Head and pronotum, dorSal view; 4, ReconStruction of head and pronotum, dorSal view